Leonardo da Vinci proposed a double hull as a ship-protection concept with two layers surrounding a vessel.
A double hull places an outer shell around an inner hull, creating a space between them. That separation can reduce the chance that a collision or grounding will immediately open the vessel’s main interior. Leonardo’s notebooks contain ship designs and maritime engineering studies that include this protective principle.
The idea was far ahead of its usual application in large commercial vessels. Modern tanker rules later made double hulls especially important because the outer layer can provide additional protection against oil spills after accidents. Leonardo’s proposal was not a modern tanker design, but it shows his interest in combining naval architecture with practical safety.
A double hull is not the same as a single hull fitted with internal bulkheads. Bulkheads divide the inside of a ship; a double hull adds an additional outer layer and an intermediate space.